The real reason Camilla won't show up at Princess Eugenie's wedding.

It’s Royal wedding day! Again. Yes, in a few short hours, the Windsors/Mountbattens will be rising from their maid-made beds, dusting off their hats and consulting Princess Eugenie’s list of rules for Friday morning’s (UK time) ceremony.

While the 72-year-old’s husband, Prince Charles, will be in attendance, the Duchess has other plans. The official line from Clarence House was a “previous commitment” involving a local school harvest festival near Birkhall, Prince Charles’ Balmoral home.

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According to The Telegraph (UK), the Duchess is in fact hosting a shooting party at her home in Scotland.

Yes. A shooting party.

Instead of a family wedding. ("Sorry darling, I shan't be able to attend. I've got some mates coming over.")

An unnamed source told the paper, “The truth is that Camilla has a house party for a few friends.

“They are arriving on Friday and will be there over the weekend."

The source sagely pointed out that Princess Eugenie's wedding date was announced eight months ago, and it's unlikely the Duchess' high calibre soiree would have predated that. But even if it did...

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The snub only adds fuel to long-burning rumours of tension between Camilla, Duchess of Cornwall, and Princess Eugenie's mother Sarah Ferguson, which reportedly centres around the latter's allegiance to Princess Diana.

Of course, it's more than likely that the Duchess's "sorry but I'm busy" RVSVP will be the last thing on Princess Eugenie's mind as she marries her long-term partner, Jack Brooksbank, today.

The nuptials, which are scheduled to take place at St George's Chapel in Windsor, will get underway at 11am local time (9pm AEDT) ahead of a open-top carriage ride through the town and a reception at Windsor Castle.